Preparation and Crystallization of Syndiotactic Polystyrene/MMT nanocomposites

• Main Authors: Ying-Ling Chen, 陳盈伶
• Other Authors: Tzong-Ming Wu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/42567530936995397859

碩士 === 國立中興大學 === 材料科學與工程學系所 === 103 === Syndiotactic polystyrene (sPS), a crystalline polymer with a high melting point, exhibits four different polymorphic crystalline behavior, namely α, β, γ and δ. The α- and β-form, both containing planar zigzag chains with the all-trans conformation, can be obtained from the melt or glass state of sPS under different thermal crystallization conditions. For the γ and δ forms, the molecular chains have the helical conformation, which is strongly depended on the solution treatment. The sPS/montmorillonite (MMT) nanocomposites prepared by modified MMT were well dispered in sPS. X-ray diffraction data show the montmorillonite are intercalated into the sPS molecular chain with the interlayered spacing of 3.74 nm. TEM micrographs shows the montmorillonite was well distributed in sPS/MMT nanocomposites. XRD analysis operated from room temperature to 250℃, was perfomed to investigate the structural changes in sPS. The δ form can be obtained by supplying 1,2,4-Trichlorobenzene (TCB) in sPS. By heating the δ form above 110℃, it can be transformed to the γ form. This γ form was further transferred into the α form by heat treatment over 190℃. The in-situ FTIR results were also observed a similar transition temperature of crystallization. The results indicate that the addition of more than 2wt% montmorillonite induces α-form at room temperature. With the continuous increase of montmorillonite content, the transformation temperature was reduced from 190℃ to 130℃. TGA results revealed the thermal properties of sPS/MMT composites were improved by increasing content of MMT. DSC scans were used to investigate the nonisothermal crystallization behavior and crystallization kinetics mechanism. The addition of MMT into sPS matrices induces faster crystallization rate. These results of sPS/MMT nanocomposites shows that the addition of MMT caused heterogeneous nucleation. 1 wt% MMT-containing sPS/MMT nanocomposites shows the highest crystallization peak temperature, but the addition of more MMT into sPS matrix causes lower crystallization peak temperature. These results indicate that MMT also cause steric hindrance and reduces the transportation ability of polymer chains during crystallization processes. For nonisothermal crystallization processes, the crystallization parameters k, n and activation energy can be analyzed by using Ozawa equation to understand the influence of the addition of modified MMT into sPS.